The United States presently uses the NTSC standard for television transmissions. However, proposals have been made to replace the NTSC standard with an Advanced Television standard. For example, it has been proposed that the U.S. adopt digital standard-definition and advanced television formats at rates of 24 Hz, 30 Hz, 60 Hz, and 60 Hz interlaced. It is apparent that these rates are intended to continue (and thus be compatible with) the existing NTSC television display rate of 60 Hz (or 59.94 Hz). It is also apparent that “3-2 pulldown” is intended for display on 60 Hz displays when presenting movies, which have a temporal rate of 24 frames per second (fps). However, while the above proposal provides a menu of possible formats from which to select, each format only encodes and decodes a single resolution and frame rate. Because the display or motion rates of these formats are not integrally related to each other, conversion from one to another is difficult.
Further, this proposal does not provide a crucial capability of compatibility with computer displays. These proposed image motion rates are based upon historical rates which date back to the early part of this century. If a “clean-slate” were to be made, it is unlikely that these rates would be chosen. In the computer industry, where displays could utilize any rate over the last decade, rates in the 70 to 80 Hz range have proven optimal, with 72 and 75 Hz being the most common rates. Unfortunately, the proposed rates of 30 and 60 Hz lack useful interoperability with 72 or 75 Hz, resulting in degraded temporal performance.
In addition, it is being suggested by some in the field that frame interlace is required, due to a claimed need to have about 1000 lines of resolution at high frame rates, but based upon the notion that such images cannot be compressed within the available 18-19 mbits/second of a conventional 6 MHz broadcast television channel.
It would be much more desirable if a single signal format were to be adopted, containing within it all of the desired standard and high definition resolutions. However, to do so within the bandwidth constraints of a conventional 6 MHz broadcast television channel requires compression (or “scalability”) of both frame rate (temporal) and resolution (spatial). One method specifically intended to provide for such scalability is the MPEG-2 standard. Unfortunately, the temporal and spatial scalability features specified within the MPEG-2 standard are not sufficiently efficient to accommodate the needs of advanced television for the U.S. Thus, the proposal for advanced television for the U.S. is based upon the premise that temporal (frame rate) and spatial (resolution) layering are inefficient, and therefore discrete formats are necessary.
In addition to the above issues, the inventor has identified a need to protect and manage the use of valuable copyrighted audio and video media such as digital movies. The viability of entire technologies for movie data delivery can hinge on the ability to protect and manage usage. As the quality of digital compressed movie masters approaches that of the original work, the need for protection and management methodologies becomes a crucial requirement.
In approaching a system architecture for digital content protection and management, it would be very beneficial to have a variety of tools and techniques which can be applied in a modular and flexible way. Most commercial encryption systems have been eventually compromised. It is therefore necessary to architect any protection system to be sufficiently flexible as to adapt and strengthen itself if and when it is compromised. It is also valuable to place informational clues into each copy via watermarking of symbols and/or serial number information in order to pinpoint the source and method by which the security has been compromised.
Movie distribution digitally to movie theaters is becoming feasible. The high value copies of new movies have long been a target for theft or copying of today's film prints. Digital media such as DVD have attempted crude encryption and authorization schemes (such as DIVX). Analog cable scramblers have been in use from the beginning to enable charging for premium cable channels and pay-per-view events and movies. However these crude scramblers have been broadly compromised.
One reason that digital and analog video systems have tolerated such poor security systems is that the value of the secondary video release and the loss due to pirating is a relatively small proportion of the market. However, for digital first-run movies, for valuable live events, and for high resolution images to the home and business (via forms of HDTV), robust security systems become a requirement.
The present invention overcomes these and other problems of current digital content protection systems.